1. Field of the Invention
The present invention relates to a valve operating system for an internal combustion engine wherein a support shaft supporting in a rotatable manner a roller which is in rolling contact with a valve operating cam is fitted in a fitting bore provided in a rocker arm, an engage groove which extends in a direction tangential to an imaginary circle about the axis of the aforementioned support shaft is provided on the outer surface of the aforementioned support shaft, and a pin engaging with the aforementioned engage groove is fixed in the aforementioned rocker arm.
2. Description of the Prior Art
In the art, such valve operating system is already known from Japanese Patent Application Laid-open No. 10-73009, etc.
In such valve operating system, the engagement of the pin, which is fixed in the rocker arm, with the engage groove on the support shaft prevents the support shaft from moving in its axial direction and rotating about its axis, and for the case above in the art the pin is press-fitted into a press-fit bore provided in the rocker arm so as to fix the pin in the rocker arm. However, in comparison with the support shaft which supports the roller in a rotatable manner, the pin has a smaller diameter and the press-fit bore also has a small diameter, and it is therefore difficult to enhance the precision of the internal diameter of the press-fit bore and the precision of the press-fit allowance of the pin. As a result, it is difficult to say that the operability of press-fitting a pin is excellent. Moreover, if the press-fit load against the pin is increased in order to effectively prevent it from falling out, a large load is applied to the rocker arm which is undesirable in terms of ensuring the rigidity of the rocker arm.